Control circuits for auxiliary light source for use with high intensity discharge lamps

ABSTRACT

The present invention relates to control circuits for auxiliary lamps which provide supplemental lighting during the start-up and cool-down phases of operation of associated high intensity discharge lamps. In a first embodiment, a control circuit is disclosed which utilizes only a single reed switch for controlling the auxiliary lamp during both the start-up phase and the cool-down phase of the high intensity discharge lamp. In several other embodiments, inductors are used which are responsive to selected currents and/or voltages to control the operation of the auxiliary lamp. In these other embodiments, a failsafe control is provided which turns off the auxiliary lamp in the event that the principal control circuit fails to do so when the high intensity discharge lamp is in a normal operating phase.

[l 1] 3,927,348 4st Dec. 16, 1975 United States Patent Zawadski S, Price, Auxiliary and Supplemental Lighting Circuits for Use with High Intensity Disch. L.Ps."

[75f Inventor: Andrzej Zawadski, Birmingham, Primary Examiner-Nathan Kaufman Attorney, Agent, or Firm-Hamess, Dickey & Pierce [73] Assignee: Rarn Meter, Inc., Ferndale, Mich.

[22] Filed:

ABSTRACT July 17, 1973 211 Appl. No.: 379,935

The present invention relates to control circuits for auxiliary lamps which provide supplemental lighting during the start-up and cool-down phases of operation of associated high intensity discharge lamps. In a first embodiment, a control circuit is disclosed which uti- Iizes only a single reed switch for controlling the auxiliary lamp during both the start-up phase and the cooldown phase of the high intensity discharge lamp. In several other embodiments, inductors are used which {56] References Cited UNITED STATES PATENTS are responsive to selected currents and/or voltages to control the operation of the auxiliary lamp. In these 3 lS/9l 3 lS/98 other embodiments, a failsafe control is provided which turns off the auxiliary lamp in the event that the 3 9 I s I 3 3,517,254 6/1970 McNamara, 3,536,954 lO/l970 Haymaker et al. 3,599,036 8/l9,7l Haymaker......... 3,6l 1,432 l0/l97l Babcock et al. FOREIGN PATENTS OR APPLICATIONS principal control circuit fails to do so when the high intensity discharge lamp is in a normal operating phase.

377,937 7/l964 Switzerland........................... 3l5/92 49 Claims, 13 Drawing Figures L .W 7 w 5 10 w mm Cw Rr m n T n E g .m a .m m m U.S. Patent Dec. 16,1975 Sheet10f4 3,927,348

U.S. Patent Dec. 16, 1975 Sheet 2 of4 3,927,348

U.S. Patent Dec. 16, 1975 Sheet30f4 3,927,348

L l E U.S. Patent Dec. 16, 1975 Sheet 4 of4 3,927,348

CONTROL CIRCUITS FOR AUXILIARY LIGHT SOURCE FOR USE WITH HIGH INTENSITY DISCHARGE LAMPS BACKGROUND AND SUMMARY OF THE INVENTION The present invention provides control circuits for auxiliary lamps which are particularly suitable for use in combination with high intensity discharge lamps to provide supplemental lighting during the start-up and cool-down phases of operation of an associated high intensity discharge lamp. In this regard, high intensity discharge lamps require a certain warm-up period, e. g. approximately 5 minutes, before the light output of the high intensity lamp reaches usable levels. Additionally. if a supply voltage drop is experienced, the high intensity discharge lamp will extinguish and will not again reach a usable light output level until after a substantial cool-down period and subsequent restart period. e.g. an accumulative period of approximately minutes. In many applications for these high intensity discharge lamps. these periods of low luminescence of the high intensity discharge lamp are not of substantial impor tance. However, in certain applications for these lamps, the initial period prior to the attainment of full luminescence and the period subsequent to a supply voltage drop in which the lamp is extinguished can result in substantial inconvenience. More importantly. in hospitals, supermarkets, and department stores, sudden light failure resulting from a supply voltage drop can cause patients or patrons to panic, thereby exposing themselves or others to injury.

With the above drawbacks of the high intensity discharge lamp in mind, control circuits for auxiliary lamps have been provided to automatically operate the auxiliary lamp when the high intensity discharge lamp is in a low luminescence condition. The present invention provides improved circuits for controlling such auxiliary lamps.

In the first exemplary embodiment of the present invention, a single reed switch is used which is responsive to the voltage across the high intensity discharge lamp. When the lamp voltage is below a first preselected level or above a second higher preselected level, the reed switch closes a gating circuit for a controlled conduction device. tag. a triac, which connects the auxiliary lamp to a supply voltage thereby lighting the auxiliary lamp. The first preselected voltage level is selected to be below the normal operational voltage of the high intensity discharge lamp during warm-up while the second preselected voltage level is selected to be above the normal operational voltage of the high intensity discharge lamp voltage during cool-down. During intermediate voltages which occur during the normal operation of the high intensity discharge lamp, the reed switch is held open so that the controlled conduction device is nonconductive to disconnect the auxiliary lamp from the supply voltage. More particularly, a reed switch is provided in combination with a permanent magnet or other magnetic source which normally bi ases the reed switich contacts to a closed position. and an electromagnet which is responsive to the voltage across the high intensity discharge lamp. When the voltage across the high intensity discharge lamp exceeds the first preselected level. the electromagnet provides a flux in opposition to the permanent magnet flux to open the contacts of the reed switch. When the 2 voltage across the high intensity discharge lamp is above the second higher preselected voltage. the electromagnet flux is effective not only to overcome the permanent magnet flux but to provide an excessive level of flux which closes the contacts of the reed switch.

In a second exemplary embodiment, the control cir cuit for the controlled conduction device includes a pair of mutually coupled control coils with one being connected to receive the current through the high intensity discharge lamp and the other being connected to receive the voltage across the high intensity discharge lamp. The control coils are wound in opposition and have a turns ratio so as to be responsive to levels of current through the high intensity discharge lamp and voltage across the high intensity discharge lamp which are representative of either the start'up phase or the cool-down phase to provide a gate signal at the controlled conduction device to light the auxiliary lamp. When the current through the high intensity lamp and the voltage across the high intensity discharge lamp are at levels characteristic of normal operation of the high intensity discharge lamp, the control coils remove the gate signal at the controlled conduction device to extin guish the auxiliary lamp.

The second embodiment of the control system of this invention is effective to turn on the controlled conduc tion device for a portion of each cycle of the alternating current supply to provide power to the auxiliary lamp during that portion. This on portion is varied generally in inverse relationship with the luminescence of the high intensity discharge lamp so that the luminescence of the auxiliary lamp is advantageously reduced as the luminescence of the high intensity discharge lamp increases.

In the second embodiment, a failsafe control is provided which assures that the auxiliary lamp does not remain lit during normal operation of the high intensity discharge lamp. In this regard, it is desirable that the total heat input to the fixture from the high intensity discharge lamp and the auxiliary lamp and the total current to the high intensity discharge lamp and the auxiliary lamp be limited to correspondingly limit the heat dissipation and temperature resistance requirements of the lamp fixture, and the current carrying requirements of the wiring to the lamp fixture, respectively. A fixture designed to safely accommodate the combined heat outputs of both the auxiliary lamp and the high intensity discharge lamp will be cumbersome and expensive relative to a fixture designed to accommodate the heat output of only one lamp for any extended period. Moreover, the current carrying requirements of the wiring leading to and within the fixture will be increased to correspondingly increase the cost of the installation and fixture. An exemplary failsafe feature used with this embodiment has a pair of mutually coupled coils, one of which is responsive to the current through the high intensity discharge lamp while the other is responsive to the voltage across the auxiliary lamp. The failsafe coils are thermally coupled to a temperature responsive switch which is connected in series with the auxiliary lamp and which is designed to open to turn off the auxiliary lamp if the auxiliary lamp is still fully on after the high intensity discharge lamp current has been at normal operating levels for a predetermined period of time.

In a third exemplary embodiment of the present invention, a pair of mutually couple control coils are provided for controlling a control conduction device which connects the auxiliary lamp to the supply voltage. The control coils are responsive to the phase relationship and amplitude between the voltage across the high intensity discharge lamp and the supply voltage. A phase shift network is used so that the phase of either the high intensity discharge lamp voltage or the supply voltage is altered prior to its provision to the control coils so that the phases and amplitudes of the supply and lamp voltages received by the coils will be in cancelling gopposition when the high intensity discharge lamp is in normal operation and so that the phases and amplitudes of the supply and lamp voltages received by the coils will be in reinforcing cooperation when the high intensity discharge lamp is in a start-up or cooldown mode. The coils are operative to gate the controlled conduction device when the phases and amplitudes are in cooperative cooperation, i.e., aiding relationship, so that the auxiliary lamp will receive current during the start-up or cool-down period of the high intensity discharge lamp. More specifically, the controlled conduction device is gated for increasing portions of the alternating current cycle in inverse relationship with the luminescence of the high intensity discharge lamp as previously described. A failsafe feature is also provided in this embodiment which includes three mutually coupled coils, one of which is connected across the auxiliary lamp to be responsive to auxiliary lamp voltage, another of which is connected across the ballast opposite the high intensity discharge lamp to be responsive to the ballast voltage and a third of which is utilized as an output coil having an impedance determined in accordance with the relationship between auxiliary lamp voltage and the ballast voltage. More specifically, the flux provided by each of the first two coils is balanced by the flux provided by the other when the auxiliary lamp is on and the ballast voltage is at a level indicating that the high intensity discharge lamp is either in the start-up phase or the cool-down phase so taht the impedance of the output coil is high, and conversely, the flux provided by each of the first two coils is not balanced by the flux provided by the other when the auxiliary lamp is on and the ballast voltage is at a level indicating that the high intensity discharge lamp is also on so that the impedance of the output coil is low. The output coil is connected in series with a heating resistor for a temperature responsive switch which receives a heating current from the auxiliary lamp potential so that if the auxiliary lamp is fully on and the high intensity discharge lamp is also fully on, the heating current resulting from the low impedance across the output coil is sufiicient to open the temperature responsive switch thereby opening the supply circuit for the auxiliary lamp to extinguish the auxiliary lamp.

In a fourth exemplary embodiment. a controlled conduction device control circuit is incorporated as described with respect to the third exemplary embodiment. However, a modified failsafe circuit is utilized a saturable-core inductor which is connected to receive the auxiliary lamp voltage and which is thermally associated with a temperature responsive switch. The response of the saturable-core inductor RMS value of the voltage across the auxiliary lamp is nonlinear so that as the RMS values oflamp voltage increases, as the on" time increases. the impedance across the saturablecore inductor decreases at an increasing rate. If the lamp is continuously on, the impedance of the satura ble-core inductor will be low so as to provide a heating current which will open the temperature responsive switch after a predetermined time period thereby disconnecting the auxiliary lamp from the power supply. The predetermined heating time period allows for normal start-up time or cool-down time. A partial operation of the auxiliary lamp indicating that the controlled conduction device is operative will yield much lower currents through the saturable-core inductor, and therefore, the temperature responsive switch is heated at a lower rate which prevents the temperature responsive switch from attaining its set opening temperature so that the auxiliary lamp remains under the control of the controlled conduction device.

In a fifth exemplary embodiment, a controlled conduction device control circuit and a failsafe circuit having a saturable-core inductor are used which are similar to those described with respect to the fourth exemplary embodiment. However, in the fifth exemplary embodiment, one of the control coils receives a signal derived from the voltage across the auxiliary lamp as well as the line voltage so that the control coils are additionally responsive to the auxiliary lamp voltage. Furthermore, a gating circuit for the controlled conduction device is used which has a capacitive voltage divider for providing a suitably shaped gating signal. The gating circuit further includes a clamping circuit having a diac for altering the gating signal under high gating voltage conditions so that the controlled conduction device will not be fully on during the cooldown time for the high intensity discharge lamp. These high gating voltage conditions exist when certain high intensity discharge lamps are used, for example, the metal-arc variety which have high cool-down voltages which result in high average levels of the gating voltages which tend to keep the controlled conduction device on at all times to provide sufficient heating of the temperature responsive switch to cause opening of the switch thereby prematurely turning off the auxiliary lamp.

In a sixth exemplary embodiment, a control circuit is used as described with respect to the fifth exemplary embodiment except that the gating is modified by the elimination of the clamping circuit and the addition of a second controlled conduction device which is connected in series with a resistor to the gate of the main controlled conduction divice to more accurately control the conduction angle of the main controlled conduction device.

Other features and advantages of the control circuits of the present invention will become apparent in view of the Detailed Description of the Preferred Embodiments hereinafter.

BRIEF DESCRIPTION OF THE DRAWlNGS FIG. 1 is a circuit diagram of a first exemplary embodiment of a control circuit according to the present invention for an auxiliary lamp;

FIG. 2 is a graphical representation of typical values of the current through a high intensity discharge lamp and the voltage across the high intensity discharge lamp during the start-up phase, normal operating phase, and cool-down phase of the high intensity discharge lamp;

FIG. 3 is a circuit diagram of a second exemplary embodiment of a control circuit according to the present invention for an auxiliary lamp;

FIGS. 40. 4b, 4c are a graphic illustration of the duty cycle of the auxiliary lamp during the increasing luminescence of high intensity discharge lamp;

FIG. 5 is a circuit diagram of a third exemplary embodiment of a control circuit according the the present invention for an auxiliary lamp;

FIGS. 60, 6b, 6c are a graphic illustration of control signals of the embodiment of FIGS. 5 and 7;

FIG. 7 is a circuit diagram of a fourth exemplary embodiment of a control circuit according to the present invention for an auxiliary lamp;

FIG. 8 is a circuit diagram of a fifth exemplary embodiment of a control circuit according to the present invention for an auxiliary lamp; and

FIG. 9 is a circuit diagram of a sixth exemplary embodiment of a control circuit according to the present invention for an auxiliary lamp.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, an exemplary embodiment of an auxiliary lighting control circuit 10 is illustrated in combination with a high intensity discharge lamp l2 and an incandescent lamp 14. The high intensity discharge lamp 12, which may be a mercury vapor lamp, a metal arc lamp, or the like, is seen to be connected to the usual ballast l6 and capacitor 18 which in turn are connected to a suitable ac. power supply at terminals 20. The ballast l6 and the capacitor 18 provide a suitable operating current and voltage for the high intensity discharge lamp 12 in the well known manner, and therefore, the function thereof will not be presented here.

The control circuit 10 includes a triac 24 which is connected in series with the auxiliary light 14 between the supply temiinals so that the auxiliary light 14 will be lit when the triac 24 is conductive. The triac 24 has a gate circuit 26 which includes a gate resistor 28 and a reed switch 30 which is effective to deliver a gating signal to the triac 24 through the resistor 28 and the reed switch 30 to fire the triac 24 when the contact of the reed switch 30 are closed. A sensing circuit 32 is connected to receive the voltage across the high intensity discharge lamp 12 at terminals 34. The control circuit 32 includes a diode bridge full wave rectifier 36 which provides a dc. voltage at terminals 38 which represents the high intensity discharge lamp voltage. The voltage across terminals 38 is filtered by a suitable capacitor 40.

The reed swich is normally held closed by the magnetic flux provided by a permanent magnet 42 which is mounted in close proximity to the reed switch 30. If desired. the premanent magnet 42 may be replaced by an electromagnetic coil. An electromagnetic coil 44 receives the rectified voltage at terminals 28 and is connected so that current therethrough provides a mgnetic field in the proximity of the reed switch 30 which is in opposition to the magnetic field of the permanent magnet 42.

The operation of the control circuit 10 of FIG. I will be explained with reference to FIG. 2 in which the current and voltages for typical start-up, cool-down, and normal periods of operation of a high intensity discharge lamp are illustrated. In this regard, FIG. 2 is not to be taken as representative of actual values of voltages and currents for any particular lamp, but merely generally representative of typical relative values of these lamps. During the start-up period, it can be seen that the voltage across the high intensity discharge lamp 12 (as indicated by the solid line) is low. The low voltage condition is sensed by the sensing circuit 32 since the voltage across the coil 44 will not sufficient to overcome the flux of the permanent magnet 42 which holds the contact of the reed switch 30 in a closed position. Consequently, the triac 24 will be conductive so as to light the auxiliary lamp 14. As the luminescence of the high intensity discharge lamp 12 reaches a near-normal level, the voltage across the high intensity discharge lamp 12 reaches a first preselected value at which the current through the coil 44 is sufficient to provide a flux in opposition to the flux of the permanent magnet 42 which neutralizes that flux to allow the contacts of the reed switch 30 to open thereby opening the gate circuit of the triac 24. Consequently, the triac 24 will turn ofi', thereby turning off the auxiliary lamp 14. If the power to the high intensity discharge lamp 12 is interrupted as illustrated in FIG. 2, the high intensity discharge lamp 12 will be extinguished resulting in a voltage across the high intensity discharge lamp [2 which exceeds a second higher preselected value as illustrated in FIG. 2. The high voltage condition causes a high current through the coil 44 yielding flux of sufficient magnitude so as to not only overcome the flux provided by the permanent magnet 42 but provide sufficient excess flux in the reverse direction to again close the contacts of the reed switch 30 thereby again providing gate current to the triac 24 to light the auxiliary lamp 14.

In FIG. 3, a second exemplary embodiment of a control system 46 for an auxiliary lamp is shown in combination with a high intensity discharge lamp 12, an incandescent auxiliary lamp 14, a ballast l6, and a capacitor 18 as previously described. The control circuit 46 is connected to the supply voltage at tenninals 48 and to the auxiliary lamp at terminal 50. The control system 46 of FIG. 3 is adapted for operation with high intensity discharge lamps 12 of two different voltages. voltaages. More particularly, a low voltage high intensity discharge lamp is connected between terminals 52 and 54 of the control circuit 46 while a high voltage high intensity discharge lamp is connected between terminals 52 and 56. In the particular embodiment shown, the high intensity discharge lamp is a low voltage lamp so that the lamp is connected between terminal 52 and 54. The connection of a high voltage high intensity discharge lamp is shown in dashed lines.

The terminal of the auxiliary lamp which is connected to terminal 50 of the control circuit 46 is connected through a temperature responsive switch 58 and a triac 60 to the supply terminal 48, which in turn is connected to the power supply at terminal 20. The other terminal of the auxiliary lamp I4 is connected to the other power supply terminal 20 so that the auxiliary lamp 14 will be lit when the temperature operated switch 58 is closed and the triac 60 is conductive.

The control circuit 46 further includes a failsafe control 64 comprising electromagnetically coupled, oppositely wound coils 68 and 70, and a principal control comprising electromagnetically coupled, oppositely wound 74 and 76. The failsafe coil 68 is connected in series with the high intensity discharge lamp 12 so as to carry the current through the high intensity discharge lamp [2. The failsafe coil 70 is connected across the auxiliary lamp 14 through the temperature responsive switch 58 so that it receives the IR voltage of the auxiliary lamp 14. The failsafe coils 68 and 70 are thermally associated with the temperature responsive switch 58 so that. under conditions to be described, the temperature responsive switch 58 will be opened through heating thereof by the current in the coils 68 and 70.

The control coil 74 is connected in series with the high intensity discharge lamp l2 and the failsafe coil 68 to carry the current through the high intensity discharge lamp l2. The principal control coil 76 is connected in series with dropping resistor 78 and a phase shift network having resistor 80 and capacitor 81 (and in the case of a high voltage discharge lamp, additionally through a phase shift network. having resistor 82 and capacitor 83, and a dropping resistor 84). The phase shift network, dropping resistor and coil 76 are connected across the high intensity discharge lamp 12 through the terminal 54 (or 56) so a phase-shift voltage waveform which is proportional to the voltage across the high intensity discharge lamp is applied across the control coil 76. The voltage at the control coil 76 is delivered to the gate of the triac 60 through a resistor 86 and a diac 88 to turn on the triac 60 when that voltage is sufficient to break down the diac 88. A capacitor 90 and a resistor 91 shape the pulses from resistor 86 to provide a wave at the diac 88 of suitable form.

The operation of the control circuit 46 will be described with reference to the graphic representations of FIGS. 2 and 4. Since the control coil 74 receives the high intensity discharge lamp current, it can be considered as sensing the current through the high intensity discharge lamp. Similarly, since the control coil 76 has a current flow therethrough which is representative of the voltage across the high intensity discharge lamp 12, it can be considered as sensing the voltage across the high intensity discharge lamp l2. Normally, the current through the high intensity discharge lamp l2 and the voltage across the high intensity discharge lamp 12 are out of phase. However, the phase shift network comprising resistor 80 and capacitor 81 (and resistor 82 and capacitor 83 for higher voltage high intensity discharge lamps) alters the phase of current through the voltage sensing coil 76 so that the current through the current sensing coil 74 and the voltage sensing coil 76 are substantially in phase.

When the high intensity discharge lamp is in the start-up phase. the current through the high intensity discharge lamp is high as can be seen in FIG. 2. Hence, the current through the current sensing coil 74 is also high so that a voltage is induced across the voltage sensing coil 76 which appears at the resistor 86 and which is sufficient to gate the triac 60 through the diac 88 so that the auxiliary lamp 14 receives the supply voltage for the entire cycle thereof as shown in FIG. 4a. It should be noted that a voltage across the voltage sensing coil 76 is also provided by virtue of the voltage across the high intensity discharge lamp 12. However, this voltage is quite low during the start-up phase, and consequently, it would not be sufficient in and of itself to gate the triac 60.

When the high intensity discharge lamp 12 is near full brilliance, the current through the high intensity discharge lamp 12 which is received by the current sensing coil 74 and the voltage across the high intensity discharge lamp 12 which is received by the voltage sensing coil 76 are at intermediate levels. The coils 74 and 76 are wound in opposition so that the currents through the current sensing coil 74 and the voltage sensing coil 76 oppose each other and cancel each others effect so that the impedance of the voltage sensing coil 76 is efi'ectively low. As a result, the volt age delivered to the diac 88 is below the breakdown voltage of the diac 88 during an initial portion of each half of the supply voltage cycle. This can be best seen by reference to FIG. 4/). As the average value of the voltage at the voltage sensing coil 76 decreases, the instantaneous value of the voltage at the coil 76 does not attain a sufficient value to break down the diac 88 to fire the triac until the supply voltage has reached a certain level as indicated by the transition between the dashed sinewave portion and the solid sinewave portion. Consequently, the auxiliary lamp 14 does not receive the full waveform of the supply voltage which effectively reduces the RMS value of the power delivered to the auxiliary lamp 14 so as to effectively reduce its luminescence. As the average value of the voltage at the voltage sensing coil 76 additionally decreases, the instantaneous value of the voltage at the coil 76 does not attain a sufficient value to break down the diac 88 to tire the triac 60 until the peaks of the supply voltage waveform are reached as shown in FIG. 40 thereby further reducing the RMS value of the power delivered to the auxiliary lamp l4, and consequently, further reducing the luminescence thereof. Upon yet additional reduction in the average value of the voltage at the voltage sensing coil 76, the diac does not receive an instantaneous value of voltage sufficient to break it down, and therefore, the triac 60 remains of? for the full supply voltage cycle so that the auxiliary lamp is fully turned off.

In view of the above explanation, it will be appreciated that the conduction angle of the triac 60 decreases as the average value of the voltage at the voltage sensing coil 76 decreases, and as a result, the luminescence of the auxiliary lamp 14 decreases. At this same time, the luminescence of the high intensity discharge lamp 12 is increasing so that the overall luminescence from the light fixture having the high intensity discharge lamp l2 and the auxiliary lamp 14 is controlled in an advantageous manner.

If a power interruption is experienced, and consequently, the high intensity discharge lamp 12 is extinguished, the current flow through the high intensity discharge lamp l2 and the current sensing coil 74 will be terminated while the voltage across the high intensity discharge lamp 12 which is received by the voltage sensing coil 76 will be high, as illustrated in FIG. 2. Consequently, a high voltage will be delivered to the gate of the triac 60 through the resistor 86 and the diac 88 to fire the triac 60 and light the auxiliary lamp 14. When the cool-down cycle ends, a start-up cycle begins at which time the auxiliary lamp [4 remains on and is controlled in accordance with the current and voltage conditions as previously described with respect to the startup cycle.

The control circuit 46 of FIG. 3 also includes a failsafe provision to turn off the lamp 14 in the event of a malfunction of the control circuit 46. In this regard, it will be appreciated that if both the high intensity discharge lamp 12 and the auxiliary lamp 14 are on simultaneously for long periods of time, the heat generation within the lamp structure containing the high intensity discharge lamp l2 and the auxiliary lamp 14 will be substantially increased. If a failsafe provision is not provided, the lamp must be designed to accommodate this substantially increased heat generation and the wiring thereto and therewithin must be increased in current carrying capacity to accommodate the substantially increased average current thereby adding to the expense of the lamp unit.

During the start-up sequence, the high current which flows through the high intensity discharge lamp 12 also flows through the failsafe coil 68. The IR drop across the auxiliary lamp 14 causes a current to flow through the failsafe coil 70 which, therefore, senses the voltage across the auxiliary coil. The current through the voltage sensing coil 70 is substantially out of phase with the current through the current sensing coil 68 during the start-up operation of the high intensity discharge lamp. As a result, the impedance of the voltage sensing coil 70fls effectively high so that the current through the coil 70 is relatively low. The high current through the current sensing coil 68, and the relatively low current through the voltage sensing coil 70 tends to heat the temperature sensitive switch 58, but at a sufiiciently low rate that the temperature responsive switch 58 does not open during the start-up cycle. Once the high intensity discharge lamp 12 nears full brilliance, the current through the current sensing coil 68 is reduced in value, but is also changed in phase, so that it more nearly matches the phase of the current through the voltage sensing coil 70. The fluxes generated by the coils are in opposition so that the substantially in phase currents through the current sensing coil 68 and the voltage sensing coil 70 establish a much lower impedance across the voltage sensing coil 70 which results in a much higher current flow through the coil 70 in response to the IR drop of the auxiliary lamp 14. The higher current flow through the voltage sensing coil 70, when combined with the current flow through the current sensing coil 68, provides a rate of heating of the temperature responsive switch 58 which is effective to open the temperature responsive switch 58 after a predetermined time period thereby opening the current path through the auxiliary lamp 14 to turn off the auxiliary lamp (if such action had not already been accomplislred by the turning off of the triac 60 under the control of the sensing coil 76). During cool-down period, the current through the high intensity discharge lamp is reduced to zero so that the rate of heating of the temperature responsive switch 58 is not sufficient to cause the switch 58 to open to interrupt the current path for the auxiliary lamp 14.

In FIG. 5, yet another exemplary embodiment of an auxiliary lamp control circuit according to this invention is illustrated. The control circuit 94 of FIG. is adapted to be connected to the auxiliary lamp 14 at the terminal 96, one line voltage terminal 20 at a terminal 98, the ballast side of the high intensity discharge lamp at a terminal 100, and the other line voltage terminal 20 at a terminal 102. The auxiliary lamp 14 will be lit when the switch 104 is closed and the triac 106 is conductive. The IR drop across the auxiliary lamp 14,

appearing between terminals 96 and 98, is imposed across a series connection of a dropping resistor 112 and a full wave diode bridge 114. The output of the full wave diode bridge 114 is impressed across a first primary coil 116 of a failsafe control 118. The failsafe control 118 further includes a second primary coil 120 and a secondary coil 122 which are inductively coupled to each other and the first primary coil 1 16. A second full wave diode bridge 124 is connected in series with a dripping resistor 126 across the ballast 16 between tle supply terminal and the high intensity discharge lamp 12 to receive a voltage related to the operating condition of the high intensity discharge lamp 12. The output of the full wave bridge 124 is connected across the second primary coil 120. The secondary coil 122 is connected in series with a heating resistor 128 and the auxiliary lamp 14. The heating resistor 128 is thermally that the temperature responsive switch 104 will be opened in response to a preselected magnitude of current through the heating resistor 128.

A principal control 130 has a first coil 132 and a second inductively coupled coil 134. The first coil 132 is connected in series with a dropping resistor 136 across the high intensity discharge lamp 12 to receive the operating voltage thereof while the second coil 134' is connected to the power supply tenninal 20 through a phase shift network 136. The phase shift network 136 includes a resistor 138 which is connected in parallel with the series combination of a resistor 140 and a capacitor 142. The voltage intermediate the resistor 136 and the first coil 132 is connected through a dropping resistor 144 to a diac 146 which in turn is connected to the gate of the triac 106. The diac 146 is also connected to a shaping capacitor 148.

The operation of the control circuit 94 of FIG. 5 will be explained with reference to FIG. 6. When the high intensity discharge lamp 12 is in the start-up phase, the voltage waveform across the high intensity discharge lamp 12 is substantially in phase with the supply voltage as shown in FIG. 60. However, the phase shift network 136 shifts the phase of the voltage waveform applied to the supply coil 134 so that the voltage across the supply coil 134 is out of phase with the voltage across the high intensity discharge coil 132. This out of phase relationship between the voltage waveforms across the lamp and supply coils 132 and 134 prevents full cancellation of the flux generated by each coil. As a result, the impedance of the lamp coil 132 is high so that a sufficient voltage is provided to the diac 146 through the resistor 144 to gate the triac 106 thereby completing the current path through,the auxiliary lamp 14.

During the normal operation of the high intensity discharge lamp 12 a distorted voltage wavefonn appears across the lamp coil 132 which is out of phase with the supply voltage wavefonn. However, the supply voltage phase is altered by the phase shift network 136 so that the waveform appearing across the supply coil 134 is substantially in phase with the waveform across the lamp coil 132. Consequently, the effective impedance of the coil 132 is low thereby pulling down the potential delivered to the diac 146 below its breakdown voltage to turn off the triac 106 and to extinguish the auxiliary lamp 14. It should be noted that the phase transition of the high intensity discharge lamp voltage is gradual to provide a gradual decrease in the impedance of the coil 132 which pulls down the average value of the voltage delivered to the diac 146 in a gradual manner. Since the instantaneous value of the voltage delivered to the diac 146 will be below its breakdown voltage during an initial portion of each half cycle which is varied in acordance with the average value of the voltage at the diac 146, the conduction angle to the triac 106 will be modulated. For that reason, the auxiliary lamp l4 transitions from full on" to full off" in the manner described with respect to FIGS. 3 and 4.

If the line power is interrupted, and as a result, the high intensity discharge lamp 12 is extinguished, the voltage waveform appearing across the high intensity discharge lamp will be substantially degrees out of phase with the supply potential waveform as shown in FIG. 6c. The phase shift network 136 is designed so that it does not provide a sufficient phase shift to bring the supply voltage waveform into phase with the wave form across the high intensity discharge lamp l2.

Therefore, the voltage waveforms seen by the lamp and supply coils I32 and 134 will be out of phase so that the effective impedance of the primary coil 132 will be high. As a result, the voltage delivered to the diac 146 through the resistor 144 will be sufficient to break down the diac 146 to turn on the triac 106 to complete the current path for the auxiliary lamp 14.

A failsafe feature which prevents operation of both the auxiliary lamp 14 and the high intensity discharge lamp 12 for an extended period of time is provided by the failsafe control 118. More particularly, the first primary coil 116 of the failsafe control 118 receives a dc. current which is related to the 1R voltage drop across the incandesent lamp 14, and hence, one which is related to the degree that incandescent the lamp 14 is one, while the coil 120 receives a dc. current related to the voltage across the ballast 16. The voltage across the ballast 16 is generally high if the high intensity discharge lamp 12 is in the start-up phase or the cooldown phase, for example, 1 volts and 130 volts, respectively, and low if the high intensity discharge lamp 12 is in the normal operational phase, for example, 80 volts. The values of resistors 112 and 126 are selected so that the currents in coils 116 and 120 due to the auxiliary lamp voltage and the ballast voltage, respectively, will be approximately the same when the high intensity discharge lamp 12 is in its start-up phase or its cool-down phase and the auxiliary lamp is on, so that there will be flux cancellation in the core common to the coils 116 and 120. When there is such flux cancellation, the effective impedance of the coil 122, which is connected in series with heating resistor 128, will be high so that the current through the coil 122 and the heating resistor 128 due to the IR voltage drop across the auxiliary lamp 14 will be low. Consequently, when the high intensity discharge lamp 12 is in the start-up or the cool-down phase and the auxiliary lamp is on, a low rate of heating of the temperature responsive switch 104 by the heating resistor 128 occurs. This low rate of heating is not sufiicient to provide a temperature which is high enough to open the thermally responsive switch 104, and consequently, the current patlhfor the auxiliary lamp 14 is not interrupted. When the igh intensity discharge lamp 12 is in its normal phase and the auxiliary lamp is on, the current through the coil 120 is low whereby an unbalanced flux exists in the core 118 from the current through coil 116. Consequently, the impedance of the coil 122 is effectively reduced whereby the current through the coil 122 and the heating resistor 128 in response to an IR voltage drop across the auxiliary lamp 14 will be high. This high current is sufiicient to provide a temperature which is high enough to open the temperature responsive switch 104 so as to interrupt the power supply to the auxiliary lamp 14. Therefore, when the high intensity discharge lamp I2 is in the normal operating phase, should the triac 106 or the control circuit fail, the failsafe control 118 will open the current path for the auxiliary lamp 14 to turn ofi' the auxiliary lamp 14.

In FIG. 7, yet another exemplary embodiment of a control system according to the present invention is illustrated. The control system 150 of FIG. 7 includes many of the components of the control system 94 of FIG. 5 which perform like functions and which are given like numbers. The control system 150 differs from the control system 94 of FIG. 5 in that a saturable core coil 151 which is thermally coupled to the temperature responsive switch 104 is utilized to provide the failsafe function performed by the diode bridges 114 and 124, thecoils 118, 120, and 122, and the resistor 128 of the control system 94 of FIG. 5, and in that respect, is simplified relative thereto. The coil 151 is connected across the auxiliary lamp 14 to receive the lamp IR drop. The coil 151 responds to the conduction angle of the triac 106 so that the average current therethrough increases as the conduction angle increases. Consequently, the heating provided by the coil 151 increases as the conduction angle increases so as to open the temperature responsive switch 104 when the auxiliary lamp 14 is fully on.

In the operation of the control circuit 150 of FIG. 7, the diac 106 is controlled by the principal control in the manner described with respect to FIG. 5. However, the manner in which failsafe control provided by the inductor 151 operates differs from the failsafe control of FIG. 5. In this regard, the failsafe inductor 151 is selected so that its core is saturated when the auxiliary lamp 14 is fully on. That is, the RMS value of the current through the inductor 151 resulting from the RMS value of the IR voltage drop of the auxiliary lamp 14 when it is fully on is sufficient to saturate the core of the inductor 151. As a result of this saturation, as the auxiliary lamp 14 is modulated by on-off operation of the triac 106 to provide a small decrease in the RMS value of the 1R voltage drop across the auxiliary lamp 14, the impedance of the inductor 151 is increased a disproportionately large amount to provide a large drop in current through the inductor 151. Consequently, the heating of the temperature responsive switch 104 by the inductor 151 is greatly reduced. Therefore, the heating of the temperature responsive switch 104 is nonlinearly related to the degree that the auxiliary lamp 14 is on, and p icularly, the heating increases at an increasing rate the on" time of the auxiliary lamp 14 increases. The temperature responsive switch 104 is selected so that it opens in response to heating by the coil 151 resulting from continuous fully on operation of the auxiliary lamp 14 over a preselected period of time and also so that it does not open in response to modulated operation of the auxiliary lamp 14. The preselected period of time is selected to be greater than the time required for the high intensity discharge lamp to start up, or to cool down and subsequently start up.

Considering now the start-up phase of operation of the high intensity discharge lamp 12, it will be appreciated that the auxiliary lamp 14 will initially be nearly fully on so as to cause heating of the temperature responsive switch 104 by the saturable-core inductor 151 tending to open the temperature responsive switch 104. However, prior to sufficient temperature rise which causes the temperature responsive switch 104 to open, the triac 106 begins turning off the portions of the positive and negative half cycles of the supply voltage so as to turn off the auxiliary lamp for those portions and to thereby reduce the heating of the temperature responsive switch 104 in the nonlinear fashion explained above. As a result, the temperature rise at the temperature responsive switch 104 is controlled so that the temperature responsive switch 104 will not open. If the triac 106 of the control circuit therefor were to become inoperative to cause the auxiliary lamp 14 to remain on either fully or on for alternate half cycles in the event of failure of the triac 106 in one direction only, the heating of the temperature responsive switch 104 by the saturablecore inductor 151 would continue 13 at its high rate so as to open the temperature responsive switch 104 thereby interrupting the current supply to the auxiliary lamp 14.

Considering now the possibility of a power interruption causing the high intensity discharge lamp 12 to extinguish, the auxiliary lamp 14 will operate intermittently so that the high intensity discharge lamp will progress through the cool-down phase and into the start-up phase without sufficient heating of the temperature responsive switch 104 by the saturable-core inductor 151 to cause the temperature rise necessary to open the temperature responsive switch 104. A malfunction of the triac 106 or the control circuit therefor which causes the auxiliary lamp to remain fully on would permit the saturable-core inductor 151 to heat the temperature responsive switch 104 to a temperature that causes the temperature responsive switch 104 to open to turn off the auxiliary lamp 14.

In FIG. 8, a fifth exemplary embodiment of a control circuit according to the present invention is illustrated. The control circuit 152 of FIG. 8 is adapted to be used in combination with a high intensity discharge lamp 12, an auxiliary lamp 14, a ballast 16, and a capacitor 18 as illustrated. The control circuit 152 includes terminals 96, 98, 100 and 102 as previously described, and additionally includes a terminal 153 which is adapted to be connected. as shown by a dashed connection, to a high intensity discharge lamp of higher voltage rating than the high intensity discharge lamp 12 shown connected to terminal 100. In this regard, the connection of a high intensity discharge lamp to the terminal 153 interposes a dropping resistor 155 in the path between the high voltage high intensity discharge lamp and the normal connection at terminal 100 for a lower voltage high intensity discharge lamp. The control circuit 152 includes a principal control 130 having a first coil 132 receiving the high intensity discharge lamp voltage and a second coil 134 which is connected to a phase shift network 136 having resistors 138 and 140 and capacitor 142. The phase shift network 136 functions in the manner described with respect to the embodiment of FIG. 7. However, the voltage received by the phase shift network is not only representative of the line voltage. but is also representative of the IR voltage drop across the auxiliary lamp 14. More specifically, the control circuit 152 has a saturable-core inductor 154 with an intermediate terminal 156 and end terminals 158 and 160. The end terminal 158 is connected to the phase shift network 136, the intermediate terminal 156 is connected to the line voltage, and the end terminal 160 is connected to the auxiliary lamp through a temperature responsive switch 104. Consequently, the phase shift network 142 receives a potential representative of line voltage by virtue of the connection from the end terminal 158 through a portion of the saturable-core inductor 154 to the line voltage on the intermediate terminal 156, and additionally receives an additive voltage representative of the auxiliary lamp IR drop by virtue of its connection through the saturablecore inductor 154 to the other end terminal 160. In the preferred embodiment, the saturable-core inductor 154 had 250 turns between the end terminal 158 and the intermediate terminal 156, and 2,000 turns between the intermediate terminal 156 and the other end terminal 160.

In the control circuit 152, the gating signal for the triac 106 is derived from the control coil 134 rather than the control coil 132 as disclosed in FIGS. and 7.

The gating circuit which delivers the signal from the control coil 134 to the triac 106 through the diac 148 includes a capacitive voltage divider 161 having capacitors and 162, a shaping resistor 164 which is connected in parallel with the capacitor 162, and a clamping circuit 165 having a resistor 166 and a diac 168. It should be noted that the diac 148 which provides a gating signal to triac 106 is connected to the control coil 134 through two parallel paths, a first path through the midpoint of the capacitive voltage divider 161, and a second path through the clamping circuit 165.

In the operation of the control circuit 152, the con trol coil 132 and the control coil 134 receive voltage waveforms, as shown in FIGS. 6a-6c, which are out of phase during the start-up and cool-down periods of operation of the high intensity discharge lamp 12 and which are caused to be in phase by the phase shift network 136 during the normal operation of the high intensity discharge lamp 12. When the two waveforms are out of phase, the impedance of the coil 134 is high so that a high voltage is provided to the gating circuit. Since a portion of the auxiliary lamp voltage is fed back to the coil 134, the voltage at the coil 134 which is delivered to the gating circuit will be higher if the auxiliary lamp is on than if the auxiliary lamp is off, for example, 10 to [5 volts higher in the preferred embodiment. As the result of the auxiliary lamp voltage feedback through the saturable-core inductor 154, the gating circuit can be designed so that intermittent operation of the triac 106 may be experienced during the period in which the auxiliary lamp should be fully off can be avoided to prevent flickering of the auxiliary lamp 14. More particularly, without the use of a feedback of the auxiliary lamp voltage to the control 130, it had been discovered that random pulses or noise in the gating circuit tended to occasionally pulse on the auxiliary lamp 14 causing the lamp 14 to flicker during periods that the lamp 14 should have remained off. Because of the increased gating signal provided as the feedback of the auxiliary lamp voltage as shown in the embodiment of FIG. 8, the gating circuit can be sufficiently desensitized so that, absent the auxiliary lamp voltage during the normal off periods, the random pulses or noise delivered to the gating circuit will not be sufficient to fire the triac 106.

The capacitive voltage divider 161, along with the shaping resistor 164, provide shaped pulses to the diac 148 which normally control the conduction angle of the triac 106. The clamping circuit 165 becomes effective to control the conduction angle of the triac 106 which the control circuit 152 is used with certain high intensity discharge lamps which have high voltage during the cool-down phase, for example, those high intensity discharge lamps known as metal-arc lamps. With those certain lamps, the high intensity discharge lamp potential is sufficiently high to provide a high gating voltage at the control coil 134 which tends to keep the triac 106 on during the full sinewave cycle during the cool-down stage. This fully on operation of the triac 106 keeps the auxiliary lamp 14 on at all times which may result in a current through the saturable-core inductor 154 which sufficiently heats the temperature responsive switch 104 to open the switch to interrupt the power supply to the auxiliary lamp 14 before the high intensity discharge lamp 12 reaches full brilliance. It will be appreciated that the temperature responsive switch 104 should not be opened to interrupt the operation of the auxiliary lamp 14 at any time during normal operation since the operation of the triac 106 should turn oh" the auxiliary lamp 14 when the appropriate level of luminescence of the high intensity discharge lamp 12 is reached. In this regard, the temperature responsive switch 104 should only come into operation in the failsafe mode wherein a failure in the circuit causes the auxiliary lamp 14 to stay lit after the high intensity discharge lamp 12 reaches full luminescence. Inadvertent opening of the temperature respon sive switch 104 is avoided through the incorporation of the clamping circuit 165. More particularly, as the gating voltage at the control circuit 134 reaches the abnormally high level consequent the use of those certain lamps, the diac 168 is broken down so as to partially shunt the capacitive voltage divider 161 thereby rendering the stored charges in the capacitive voltage divider 161 less effective to reduce the voltage at the diac 148. As a result, during the initial portion of each gating waveform, the potential at the diac 148 is insufficient to break down the diac 148 so that the triac is off during that portion of the gating cycle. As a result, the auxiliary lamp 14 is not operated continuously and thus premature opening of the temperature responsive switch 104 is avoided.

In FIG. 9, yet another embodiment of a control cir cuit according to the present invention is illustrated. The control circuit 170 of FIG. 9 includes many elements which are the same as like numbered elements described with respect to the control circuit 152 of FIG. 8. Since these elements operate in the manner set forth with respect to the control circuit 152 of FIG. 8, a description thereof will not be repeated.

In the control circuit 170, a capacitive voltage divider 172 having pulse shaping capacitors 174 and 176 is used which is similar in connection and operation to the capacitor voltage divider 161 of the control circuit 152 of FIG. 8. The gating circuit further includes a resistor 178 which is connected in series with a capacitive voltage divider 172 to further aid in providing gating pulses of suitable shape. The midpoint of the capacitive voltage divider is connected to a diac 180 which provides a gating signal to a control triac 182. The control triac 182 has its main terminals connected in series with a resistor 184 between the line potential on terminal and the gate of a main triac 186 so that a signal is supplied to the main triac 186 when the control triac 182 is rendered conductive by a gating signal from the diac 180. However, the main triac 186 will not fire until the waveform appearing at terminal 20 achieves an amplitude sufficient to gate the main triac 186 through the resistor 184 subsequent to the firing of the control triac 182. In this regard, the value of the resistor 184 is selected to establish the time after polarity reversal of the signal on terminal 20 at which the gating signal delivered to the main triac 186 reaches a level which is adequate to gate the main triac 186. Prior to polarity reversal at the terminal 20, the control triac 182 will be gated by breakdown of the diac 180 in response to the potential provided thereto by the shaping capacitive voltage divider 172. It has been found that the use of a control triac 182 in combination with a gating circuit is connected to receive and utilize the supply terminal voltage to provide a gating signal provides more accurate control of the conduction angle of the main triac 186 than that generally obtainable using a gating signal which is more isolated from the supply voltage waveform, for example, as by 16 the control coils and the capacitive voltage divider 161 of the control circuit 152 of FIG. 8.

In view of the above description of the preferred embodiments of the control circuits for high intensity discharge lamps according to the present invention, it will be appreciated that new circuits are disclosed which provide important operational advantages over the prior art circuits.

While it will be apparent that the preferred embodimerits of the invention herein disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation, and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. A control system for an auxiliary lamp for providing supplemental lighting for a high intensity discharge lamp, said discharge lamp being connectable to a source of electric power to establish a voltage thereacross and having a normal mode of operation in which the luminescence of said high intensity discharge lamp is at a high level and the voltage thereacross is at an intermediate level and start-up and cool-down modes of operation in which the luminescence of said high intensity discharge lamp is at a reduced level relative to said high level of luminescence and the voltage thereacross is at low and high levels, respectively, comprising:

controlled conduction means having a control terminal for receiving a control signal for connecting said auxiliary lamp to an electric power source for said auxiliary lamp to light said auxiliary lamp; and single control means connected to receive the voltage across said high intensity discharge lamp so as to be responsive to said start-up and said cooldown modes of operation of said high intensity discharge lamp for providing said control signal to said control terminal of said controlled conduction means to light said auxiliary lamp during at least portions of said start-up and said cool-down modes of operation of said high intensity discharge lamp whereby said auxiliary lamp provides supplemental lightening when the level of said luminescence of said high intensity discharge lamp is reduced, said single control means including switch means connected to said control terminal of said controlled conduction means which provides said control signal when closed and terminates said control signal when opened, and means for operating said switch including a first source of magnetic flux which has a flux magnitude which is effective to close said switch means during said start-up mode of operation, and a second source of magnetic flux which receives the voltage across said high intensity discharge lamp to provide a magnetic flux which is in opposition to said magnetic flux of said first source and which has a low flux magnitude which is ineffective to overcome said switch closing flux magnitude of said first source in response to said low voltage level across said high intensity discharge lamp representative of said start-up mode of operation of said high intensity discharge lamp so that said switch remains closed, which has an intermediate flux magnitude which is effective to overcome said switch closing flux magnitude of said first source to open said switch means in response to said intermediate voltage level across said high intensity discharge lamp representative of 1 7 said normal mode of operation of said high intensity discharge lamp, and which has a high flux magnitude which is effective to close said switch means in response to said high voltage across said high intensity discharge lamp representative of said cool-down mode of operation of said high intensity discharge lamp. 2. A control system according to claim 1 wherein said first source of magnetic flux is a permanent magnet.

3. A control system for an auxiliary lamp for providing supplemental lightipg for a high intensity discharge lamp, said high intensity discharge lamp being connectable to a source of supply voltage and having a normal mode of operation in which the luminescence of said high intensity discharge lamp is at a high level and start-up and cool-down modes of operation in which the luminescence of said high intensity discharge lamp is at a reduced level relative to said high level of luminescence comprising:

controlled conduction means having a control terminal for receiving a control signal for connecting said auxiliary lamp to an electric power source for said auxiliary lamp to light said auxiliary lamp control means including a pair of mutually coupled coils, one of said pair of coils being connected to receive the voltage across said high intensity discharge lamp and the other of said pair of coils being connected to receive said supply voltage, so as to respond to said start-up and said cool-down modes of operation of said lamp, a selected one ot said one and said other coils being further connected to said control terminal of said controlled conduction means for providing said control signal to light said auxiliary lamp, the impedance of said one coil being different during at least portions of said start-up and said cool-down modes of operation of said high intensity discharge lamp than during at least a portion of said normal mode of operation so that said selected one coil provides said control signal to said control tenninal to said controlled conduction means during said portions of said start-up and cool-down modes of operation of said high intensity discharge lamp whereby said auxiliary lamp provides supplemental lighting when the level of said luminescence of said high intensity discharge lamp is reduced.

4. A control sysem according to claim 3 further including a capacitor connected to at least one of said pair of coils for providing said control signal.

5. A control system according to claim 4 further including a second capacitor connected in series with said first mentioned capacitor for providing a voltage divider, said voltage divider providing said control signal intermediate said first mentioned capacitor and said second capacitor.

6. A control system according to claim 3 further including means for limiting the amplitude of said control signal when the voltage across said high intensity discharge lamp exceeds a predetermined voltage.

7; A control systemaccording to claim 6 wherein said limiting means is a clamping circuit which includes a voltage breakdown device fdr limiting the amplitude of said control signal.

8. A control system according to claim 7 further including a capacitor connected in parallel with clamping circuit so that said capacltoi' is shiihte'tl said clamping circuit when said control signal attains a predetermined amplitude.

.including phase-shifting means for connecting one of said coils to receive the respective one of said voltage across said high intensity discharge lamp and said supply voltage.

10. A control system according to claim 9 wherein said phase-shifting means shifts the phase of said respective one of said voltage across said high intensity discharge lamp and said supply voltage so that said voltage across said one coil is out-of-phase with said voltage across said other coil during said start-up and said cool-down mode of operation of said high intensity discharge lamp so that the impedance of said selected one coil is high, and so that said voltage across said one coil is in phase with said voltage across said other coil during said normal mode of operation of said high intensity discharge lamp so that said impedance of said selected one coil is low, said selected one coil providing said control signal to said control terminal of said first controlled conduction means when said impedance of said selected one coil is high.

11. A control system according to claim 10 wherein said phase-shifting means is connected to provide said supply voltage to said one coil.

12. A control system for an auxiliary lamp for providing supplemental lighting for a high intensity discharge lamp, said high intensity discharge lamp being connectable to a source of electric power to establish a voltage thereacross and having a normal mode of operation in which the luminescence of said high intensity discharge lamp is at a high level and start-up and cool-down modes of operation in which the luminescence of said high intensity discharge lamp is at a reduced level relative to said high level of luminescence comprising:

controlled conduction means for receiving an alternating waveform and which is connected to said auxiliary lamp for supplying at least a portion of said alternating waveform to said auxiliary lamp to light said auxiliary lamp in response to a control signal; and

control means for connection to said high intensity discharge lamp to be responsive to said start-up and said cool-down modes of operation of said high intensity discharge lamp for providing said control signal to said controlled conduction means to light said auxiliary lamp during at least portions of said one of said start-up and said cool-down modes of operation of said high intensity discharge lamp whereby said auxiliary lamp provides supplemental lighting when the level of said luminescence of said high intensity discharge lamp is reduced during said one of said start-up and said cool-down modes of operation of said high intensity discharge lamp, said control means providing said control signal for varying portions of the whole of said alternating waveform so that said auxiliary lamp receives corresponding varying portions of the whole of said alternating waveform; and

failsafe means responsive to the magnitude of the portion of said alternating waveform provided td said auxiliary lamp to prevent sustained a railBfl of said auxiliary lamp withsald auxillfli'y sins ft ceiving the whole of said lternating wsvefsirn 13. A control system aiiEordi'rifl t8 cliiiii ii WliEiElii said failsafe means is at least part responsive i8 ihE iii wage drop acioss said auxiliary lath A 14-. a c'ontrdi system weeding tae r2 whererg said hillsaie meats rrraudss a an whic rs eamrsete to said auxiliary lamp to receive the IR voltage drop across said auxiliary lamp.

is. A control system according to claim 12 wherein said failsafe means includes a coil connected to said auxiliary lamp for receiving the voltage drop thereacross having a core which approaches saturation when said auxiliary lamp receives increasing portions of said alternating waveform approaching the full alternating waveform so that there is an increasing rate of change in the impedance of said coil when said auxiliary lamp approaches continuous operation.

16. A control system according to claim 12 wherein said failsafe means includes a coil connected to said auxiliary lamp for receiving at least a portion of the voltage drop across said lamp to establish a current through said coil and which has a core which approaches saturation when said lamp receives nearly the entirety of said alternating waveform so that the impedance of said coil decreases at an increasing rate when said auxiliary lamp receives nearly the entirety of said alternating wavefonn and hence said current through said coil and the temperature rise of said coil consequent said currennt increases at an increasing rate as said auxiliary lamp receives nearly the entirety of said alternating waveform, said failsafe means further including a temperature responsive switch means in heat transfer relationship with said coil which is openable upon a predetermined temperature at said temperature responsive switch means, said temperature responsive switch means connecting said auxiliary lamp to alternating waveform so that said auxiliary lamp is turned off when said temperature responsive switch means opens, said predetermined temmperature at which said temperature responsive switch means opens being related to a predetermined temperature of said coil which is indicative of said core approaching saturation as said auxiliary lamp receives nearly the entirety of said alternating waveform so that said auxiliary lamp is turned off to prevent continuous operation thereof.

17. A control system according to claim 16 wherein said control means provides nearly the entirety of said alternating waveform to said auxiliary lamp when said hi intensity discharge lamp is in said start-up and coo -down modes of operation.

18. A control system for an auxiliary lamp for providing supplemental lighting for a high intensity discharge lamp, said high intensity discharge lamp being connectable with a source of supply voltage to establish an alternating voltage waveform thereacross and having a normal mode of operation in which the luminescence of said high intensity discharge lamp is at a high level and start-up and cool-down modes of operation in which the luminescence of said high intensity discharge lamp is at a reduced level relative to said high level of luminescence comprising:

controlled conduction means having a control tenninal for receiving a control signal for connecting said auxiliary lamp to an electric power source for said auxiliary lamp to light said auxiliary lamp; and control means receiving the voltage across said high intensity discharge lamp and a voltage waveform from said supply voltage and being responsive to the relative phase of the voltage waveform across said high intensity discharge lamp and the voltage waveform from said supply voltage for providing said control signal to said control terminal of said controlled conduction means to light said auxiliary lamp during at least portions of at least one of said start-up and said cool-down modes of operation of said high intensity discharge lamp whereby said auxiliary lamp provides supplemental lighting when the level of luminescence of said high intensity discharge lamp is reduced during said one of said start-up and said cool-down modes of operation of said high intensity discharge lamp.

19. A control system according to claim 18 further including voltage threshold breakdown means which is conductive at a predetermined voltage level for limiting the amplitude of said control signal when the voltage across said high intensity discharge lamp exceeds said predetermined voltage.

20. A control system according to claim 19 wherein said limiting means is a clamping circuit which includes a voltage breakdown device for limiting the amplitude of said control signal.

21. A control system according to claim 20 further including a capacitor connected in parallel with said clamping circuit so that said capacitor is shunted by said clamping circuit when said control signal attains a predetermined amplitude.

22. A control system according to claim 18 further including phase shift means for shifting the phase of one of said supply voltage waveform received by said control means or said voltage waveform across said high intensity discharge lamp so that said supply voltage waveform and said voltage waveform across said high intensity discharge lamp assumes a predetermined relationship during said normal mode of operation of said high intensity discharge lamp and wherein said control means provides said control signal for lighting said auxiliary lamp when said predetermined relationship does not exist.

23. A control system according to claim 18 wherein said control means is additionally responsive to the relative amplitude of the voltage waveform across said high intensity discharge lamp and the voltage waveform from said supply voltage.

24. A control system according to claim 18 wherein said control means is additionally responsive to the relative shape of the voltage waveform across said high intensity discharge lamp and the voltage waveform from said supply voltage.

25. A control system according to claim 18 wherein said control means is additionally responsive to the relative amplitude and shape of the voltage waveform across said high intensity discharge lamp and the voltage waveforrn from said supply voltage.

26. A control system according to claim 18 wherein said control means includes a pair of mutually coupled coils with one of said coils receiving at least a portion of said voltage waveform across said high intensity discharge lamp and the other of said coils receiving at least a portion of the voltage waveform from said supply voltage.

27. A control system according to claim 26 wherein one of said coils provides said control signal to said control terminal of said controlled conduction means.

28. A control system according to claim 27 wherein the impedance through said one of said coils is high for one relative phase relationship of the voltage waveform across said high intensity discharge lamp and the voltage waveform from said supply voltage and is low for another phase relationship of the voltage waveform across said high intensity discharge lamp and the voltage waveform from said supply voltage.

29. A control system according to claim 28 wherein said voltage waveform across said high intensity discharge lamp is out of phase with said voltage waveform from said supply voltage during said start-up mode and said cool-down mode of operation of said high intensity discharge lamp so that the impedance of said one coil is high. and said voltage waveform across said high intensity discharge lamp is in phase with said voltage waveform from said supply voltage during said normal mode of operation of said high intensity discharge lamp so that said impedance of said one coil is low, said one coil being connected to said control terminal of said controlled conduction device so as to turn on said controlled conduction device when said impedance of said one soil is high.

30. A control system according to claim 29 including phase-shifting means connected to receive one of the voltage waveforms of said high intensity discharge lamp and said voltage waveform from said supply voltate to provide said in-phase and out-of-phase relationships.

31. A control system according to claim 29 including phase-shifting means connected to receive said supply voltage to provide said voltage waveform from said supply voltage.

32. A control system for an auxiliary lamp for providing supplemental lighting for a high intensity discharge lamp which is adapted to be powered by a source of supply voltage through a ballast, said ballast having first, second and third terminals with said first and third terminals being adapted to be connected to said source of supply and said second and third terminals being adapted to be connected to said high intensity dis charge lamp, said high intensity discharge lamp having a normal mode of operation in which the luminescence of said high intensity discharge lamp is at a high level and start-up and cool-down modes of operation in which the luminescence of said high intensity discharge lamp is at a reduced level relative to said high level of luminescence comprising:

controlled conduction means having a control terminal for receiving a control signal for connecting said auxiliary lamp to an electric power source for said auxiliary lamp to light said auxiliary lamp; and

control means responsive to the voltage between said first and second terminals of said ballast for providing said control signal to said control terminal of said controlled conduction means to light said auxiliary lamp during at least portions of one of said start-up and said cool-down modes of operation of said high intensity discharge lamp whereby said auxiliary lamp provides supplemental lighting when the level of said luminescence of said high intensity discharge lamp is reduced during said one of said start-up and cool-down modes of operation of said high intensity discharge lamp.

33. A control system according to claim 32 wherein said control means includes a coil which received said voltage between said first and second terminals of said ballast and which is responsive thereto.

34. A control system for an auxiliary lamp for providing supplemental lighting for a high intensity discharge lamp having a normal mode of operation in which the luminescence of said high intensity discharge lamp is at a high level and start-up and cool-down modes of operation in which the luminescence of said high intensity discharge lamp is at a reduced level relative to said high level of luminescence comprising:

control means for connecting said auxiliary lamp to a source of electric power for lighting said auxiliary lamp during at least portions of said start-up and said cool-down modes of operation of said high intensity discharge lamp and to provide an IR voltage drop across said auxiliary lamp. said first control means ordinarily disconnecting said auxiliary lamp from said source of electric power during said normal mode of operation of said high intensity discharge lamp; and

failsafe means in addition to said control means which is connected to said auxiliary lamp and is at least in part responsive to the [R voltage drop across said auxiliary lamp for limiting simultaneous operation of said high intensity discharge lamp and said auxiliary lamp while under the control of said control means.

35. A control system according to claim 34 wherein said failsafe means is at least in part responsive to the current through said high intensity discharge lamp.

36. A control system according to claim 34 wherein said failsafe means includes a coil which is responsive to the [R voltage drop across said auxiliary lamp.

37. A control system according to claim 36 wherein said coil has a core which is saturable in response to an IR voltage drop across said high intensity discharge lamp when said high intensity discharge lamp is on continuously.

38. A control system according to claim 34 wherein said high intensity discharge lamp is adapted to be powered by a source of supply voltage through a ballast, said ballast having first, second and third terminals with said first and third terminals being adapted to be connected to said source of supply and said second and third terminals being adapted to be connected to said high intensity discharge lamp, said failsafe means being at least in part responsive to the voltage between said first and second terminals of said ballast for limiting simultaneous operation of said high intensity discharge lamp and said auxiliary lamp under control of said control means.

39. A control system according to claim 36 wherein said failsafe means includes a temperature responsive switch which is openable upon a predetermined simultaneous operation of said high intensity discharge lamp and said auxiliary lamp to turn off said auxiliary lamp.

40. A control system according to claim 39 wherein said failsafe means includes heating means which is responsive to the current through said auxiliary lamp for heating said temperature responsive switch when said auxiliary lamp is on.

41. A control system according to claim 40 wherein said heating means receives a current derived from at least a portion of the IR voltage drop across said auxiliary lamp.

42. A control system according to claim 40 wherein said heating means is a resistor.

43. A control system according to claim 40 wherein said heating means is a coil.

44. A control system according to claim 43 wherein said supply voltage has an alternating waveform and said auxiliary lamp continuously receives the entirety of said alternating waveform at times and receives portions of said alternating waveform at other times. and wherein said failsafe means includes a coil having a core which is saturated when said auxiliary lamp receives the entirety of said alternating waveform.

45. A control system for an auxiliary lamp for providing supplemental lighting for a high intensity discharge lamp. said discharge lamp being connectable to a source of electric power to establish a voltage thereacross and having a normal mode of operation in which the luminescence of said high intensity discharge lamp is at a high level and start-up and cool-down modes of operation in which the luminescence of said high intensity discharge lamp is at a reduced level relative to said high level of luminescence comprising:

controlled conduction means having a control terminal for receiving a control signal for connecting said auxiliary lamp to an electric power source for said auxiliary lamp to light said auxiliary lamp; and control means for connection to said high intensity discharge lamp to be responsive to said start-up and cool-down modes of opeation of said high intensity discharge lamp and further being connected to receive the voltage across said auxiliary lamp to be in part responsive to the voltage across said auxiliary lamp for providing said control signal to said control terminal of said controlled conduction means to light said auxiliary lamp during at least portions of said start-up and said cool-down modes of operation of said high intensity discharge lamp whereby said auxiliary lamp provided supplemental lighting when the level of said luminescence of said high intensity discharge lamp is reduced.

46. The control system according to claim 45 wherein said control means increases said control signal in response to a voltage across said auxiliary lamp indicating that said auxiliary lamp is lit.

47. A control system according to claim 45 wherein said voltage across said auxiliary lamp tends to maintain the provision of said control signal to said control terminal of said controlled conduction means when said auxiliary lamp is connected to said source of electric power.

48. A control system for an auxiliary lamp for providing supplemental lighting for a high intensity discharge lamp, said discharge lamp being connectable to a source of electric power to establish a voltage there- 24 across and having a normal mode of operation in which the luminescence of said high intensity discharge lamp is at a high level and start-up and cool-down modes of operation in which the luminescence of said high intensity discharge lamp is at a reduced level relative to said high level of luminescence comprising:

first controlled conduction means associated with said auxiliary lamp and a source of power for said auxiliary lamp for controlling the lighting of said auxiliary lamp, said first controlled conduction means including a control terminal for causing said first controlled conduction means to conduct to connect said source of power to said auxiliary lamp to light said auxiliary lamp in response to a first control signal at said control terminal; second controlled conduction means connected to said control terminal of said first controlled conduction means, said second controlled conduction means having a control terminal and supplying said first control signal to said control terminal of said first controlled conduction means in response to a second control signal at said control terminal of said second controlled conduction means; and control means connected to said high intensity discharge lamp to be responsive to said start-up and said cool-down modes of operation of said high intensity discharge lamp for providing said second control signal to said control terminal of said second controlled conduction means so that said second controlled conduction means supplies said control signal to said control terminal of said first controlled conduction means to light said auxiliary lamp during at least portions of said start-up and said cool-down modes of operation of said high intensity discharge lamp whereby said auxiliary lamp provides supplemental lighting when the level of said luminescence of said high intensity discharge lamp is reduced. 49. A control system according to claim 1 wherein said switch means is a reed switch.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3, 927, 348

DATED December 16, 1975 INVENT I Andrzej Zawadzki It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the cover sheet, the name of the inventor should be -ANDRZEJ ZAWADZKI.

Column 3, line ll, "gopposition" should be --opposition-; line 40, "taht" should be -that; line 58, after "utilized" insert using--; line 62, after "inductor" insert -to the-. Column 4, line 42, after "gating" insert -circuit. Column 5, line 49, "premanent" should be --permanent--;

line 53, mgnetic" should be -magnetic--; line 68, after "not" insert --be-. Column 6, line 35, after "different" insert -operating, and "voltaages" should be -voltages; line 58, after "wound" insert -coils-. Column 7, line 12, "phase-shift" should be -phaseshifted. Column 9, line 36, after "During" insert --the--; line 61, "dripping" should be -dropping-. Column 11, line 15, after "that" delete -incandescent; line 16, "one" should be -on-. Column 12, line 55, "the" second occurrence, should be for. Column 14, line 30, after "106" insert -which; line 51, "which" should be -when-. Column 15, line 12, "circuit" should be c0il--; line 63, after "circuit" insert which-. Column 17, line 40, "to", second occurrence, should be --of--. Column 18, line 65, "a" should be --in-. Column 19, line 23, "currennt" should be -current-; line 33, "temperature" should be --temperature--. Column 21, line 15, "soil" should be coil-; line 19, "voltate" should be -voltage-. Column 23, line 17, "opeation" should be --operation-; line 26, "provided" should be -provides.

Signed and Scaled this Third Day of August 1976 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner oj'Parenrs and Trademarks 

1. A control system for an auxiliary lamp for providing supplemental lighting for a high intensity discharge lamp, said discharge lamp being connectable to a source of electric power to establish a voltage thereacross and having a normal mode of operation in which the luminescence of said high intensity discharge lamp is at a high level and the voltage thereacross is at an intermediate level and start-up and cool-down modes of operation in which the luminescence of said high intensity discharge lamp is at a reduced level relative to said high level of luminescence and the voltage thereacross is at low and high levels, respectively, comprising: controlled conduction means having a control terminal for receiving a control signal for connecting said auxiliary lamp to an electric power source for said auxiliary lamp to light said auxiliary lamp; and single control means connected to receive the voltage across said high intensity discharge lamp so as to be responsive to said start-up and said cool-down modes of operation of said high intensity discharge lamp for providing said control signal to said control terminal of said controlled conduction means to light said auxiliary lamp during at least portions of said start-up and said cool-down modes of operation of said high intensity discharge lamp whereby said auxiliary lamp provides supplemental lightening when the level of said luminescence of said high intensity discharge lamp is reduced, said single control means including switch means connected to said control terminal of said controlled conduction means which provides said control signal when closed and terminates said control signal when opened, and means for operating said switch including a first source of magnetic flux which has a flux magnitude which is effective to close said switch means during said start-up mode of operation, and a second source of magnetic flux which receives the voltage across said high intensity discharge lamp to provide a magnetic flux which is in opposition to said magnetic flux of said first source and which has a low flux magnitude which is ineffective to overcome said switch closing flux magnitude of said first source in response to said low voltage level across said high intensity discharge lamp representative of said start-up mode of operation of said high intensity discharge lamp so that said switch remains closed, which has an intermediate flux magnitude which is effective to overcome said switch closing flux magnitude of said first source to open said switch means in response to said intermediate voltage level across said high intensity discharge lamp representative of said normal mode of operation of said high intensity discharge lamp, and which has a high flux magnitude which is effective to close said switch means in response to said high voltage across said high intensity discharge lamp representative of said cool-down mode of operation of said high intensity discharge lamp.
 2. A control system according to claim 1 wherein said first source of magnetic flux is a permanent magnet.
 3. A control system for an auxiliary lamp for providing supplemental lighting for a high intensity discharge lamp, said high intensity discharge lamp being connectable to a source of supply voltage and having a normal mode of operation in which the luminescence of said high intensity discharge lamp is at a high level and start-up and cool-down modes of operation in which the luminescence of said high intensity discharge lamp is at a reduced level relative to said high level of luminescence comprising: controlled conduction means having a control terminal for receiving a control signal for connecting said auxiliary lamp to an electric power source for said auxiliary lamp to light said auxiliary lamp control means including a pair of mutually coupled coils, one of said pair of coils being connected to receive the voltage across said high intensity discharge lamp and the other of said pair of coils being connected to receive said supply voltage, so as to respond to said start-up and said cool-down modes of operation of said lamp, a selected one of said one and said other coils being further connected to said control terminal of said controlled conduction means for providing said control signal to light said auxiliary lamp, the impedance of said one coil being different during at least portions of said start-up and said cool-down modes of operation of said high intensity discharge lamp than during at least a portion of said normal mode of operation so that said selected one coil provides said control signal to said control terminal to said controlled conduction means during said portions of said start-up and cool-down modes of operation of said high intensity discharge lamp whereby said auxiliary lamp provides supplemental lighting when the level of said luminescence of said high intensity discharge lamp is reduced.
 4. A control sysem according to claim 3 further including a capacitor connected to at least one of said pair of coils for providing said control signal.
 5. A control system according to claim 4 further including a second capacitor connected in series with said first mentioned capacitor for providing a voltage divider, said voltage divider providing said control signal intermediate said first mentioned capacitor and said second capacitor.
 6. A control system according to claim 3 further including means for limiting the amplitude of said control signal when the voltage across said high intensity discharge lamp exceeds a predetermined voltage.
 7. A control system according to claim 6 wherein said limiting means is a clamping circuit which includes a voltage breakdown device for limiting the amplitude of said control signal.
 8. A control system according to claim 7 further including a capacitor connected in parallel with said clamping circuit so that said capacitor is shunted by said clamping circuit when said control signal attains a predetermined amplitude.
 9. A control system according to claim 3 further including phase-shifting means for connecting one of said coils to receive the respective one of said voltage across said high intensity discharge lamp and said supply voltage.
 10. A control system according to claim 9 wherein said phase-shifting means shifts the phase of said respective one of said voltage across said high intensity discharge lamp and said supply voltage so that said voltage across said one coil is out-of-phase with said voltage across said other coil during said start-up and said cool-down mode of operation of said high intensity discharge lamp so that the impedance of said selected one coil is high, and so that said voltage across said one coil is in phase with said voltage across said other coil during said normal mode of operation of said high intensity discharge lamp so that said impedance of said selected one coil is low, said selected one coil providing said control signal to said control terminal of said first controlled conduction means when said impedance of said selected one coil is high.
 11. A control system according to claim 10 wherein said phase-shifting means is connected to provide said supply voltage to said one coil.
 12. A control system for an auxiliary lamp for providing supplemental lighting for a high intensity discharge lamp, said high intensity discharge lamp being connectable to a source of electric power to establish a voltage thereacross and having a normal mode of operation in which the luminescence of said high intensity discharge lamp is at a high level and start-up and cool-down modes of operation in which the luminescence of said high intensity discharge lamp is At a reduced level relative to said high level of luminescence comprising: controlled conduction means for receiving an alternating waveform and which is connected to said auxiliary lamp for supplying at least a portion of said alternating waveform to said auxiliary lamp to light said auxiliary lamp in response to a control signal; and control means for connection to said high intensity discharge lamp to be responsive to said start-up and said cool-down modes of operation of said high intensity discharge lamp for providing said control signal to said controlled conduction means to light said auxiliary lamp during at least portions of said one of said start-up and said cool-down modes of operation of said high intensity discharge lamp whereby said auxiliary lamp provides supplemental lighting when the level of said luminescence of said high intensity discharge lamp is reduced during said one of said start-up and said cool-down modes of operation of said high intensity discharge lamp, said control means providing said control signal for varying portions of the whole of said alternating waveform so that said auxiliary lamp receives corresponding varying portions of the whole of said alternating waveform; and failsafe means responsive to the magnitude of the portion of said alternating waveform provided to said auxiliary lamp to prevent sustained operation of said auxiliary lamp with said auxiliary lamp receiving the whole of said alternating waveform.
 13. A control system according to claim 12 wherein said failsafe means is at least a part responsive to the IR voltage drop across said auxiliary lamp.
 14. A control system according to claim 12 wherein said failsafe means includes a coil which is connected to said auxiliary lamp to receive the IR voltage drop across said auxiliary lamp.
 15. A control system according to claim 12 wherein said failsafe means includes a coil connected to said auxiliary lamp for receiving the voltage drop thereacross having a core which approaches saturation when said auxiliary lamp receives increasing portions of said alternating waveform approaching the full alternating waveform so that there is an increasing rate of change in the impedance of said coil when said auxiliary lamp approaches continuous operation.
 16. A control system according to claim 12 wherein said failsafe means includes a coil connected to said auxiliary lamp for receiving at least a portion of the voltage drop across said lamp to establish a current through said coil and which has a core which approaches saturation when said lamp receives nearly the entirety of said alternating waveform so that the impedance of said coil decreases at an increasing rate when said auxiliary lamp receives nearly the entirety of said alternating waveform and hence said current through said coil and the temperature rise of said coil consequent said currennt increases at an increasing rate as said auxiliary lamp receives nearly the entirety of said alternating waveform, said failsafe means further including a temperature responsive switch means in heat transfer relationship with said coil which is openable upon a predetermined temperature at said temperature responsive switch means, said temperature responsive switch means connecting said auxiliary lamp to alternating waveform so that said auxiliary lamp is turned off when said temperature responsive switch means opens, said predetermined temmperature at which said temperature responsive switch means opens being related to a predetermined temperature of said coil which is indicative of said core approaching saturation as said auxiliary lamp receives nearly the entirety of said alternating waveform so that said auxiliary lamp is turned off to prevent continuous opeation thereof.
 17. A control system according to claim 16 wherein said control means provides nearly the entirety of said alternating waveform to said auxiliary lamp when said high intensity discharge lamp is in said start-up and cool-down modes of operation.
 18. A control system for an auxiliary lamp for providing supplemental lighting for a high intensity discharge lamp, said high intensity discharge lamp being connectable with a source of supply voltage to establish an alternating voltage waveform thereacross and having a normal mode of operation in which the luminescence of said high intensity discharge lamp is at a high level and start-up and cool-down modes of operation in which the luminescence of said high intensity discharge lamp is at a reduced level relative to said high level of luminescence comprising: controlled conduction means having a control terminal for receiving a control signal for connecting said auxiliary lamp to an electric power source for said auxiliary lamp to light said auxiliary lamp; and control means receiving the voltage across said high intensity discharge lamp and a voltage waveform from said supply voltage and being responsive to the relative phase of the voltage waveform across said high intensity discharge lamp and the voltage waveform from said supply voltage for providing said control signal to said control terminal of said controlled conduction means to light said auxiliary lamp during at least portions of at least one of said start-up and said cool-down modes of operation of said high intensity discharge lamp whereby said auxiliary lamp provides supplemental lighting when the level of luminescence of said high intensity discharge lamp is reduced during said one of said start-up and said cool-down modes of operation of said high intensity discharge lamp.
 19. A control system according to claim 18 further including voltage threshold breakdown means which is conductive at a predetermined voltage level for limiting the amplitude of said control signal when the voltage across said high intensity discharge lamp exceeds said predetermined voltage.
 20. A control system according to claim 19 wherein said limiting means is a clamping circuit which includes a voltage breakdown device for limiting the amplitude of said control signal.
 21. A control system according to claim 20 further including a capacitor connected in parallel with said clamping circuit so that said capacitor is shunted by said clamping circuit when said control signal attains a predetermined amplitude.
 22. A control system according to claim 18 further including phase shift means for shifting the phase of one of said supply voltage waveform received by said control means or said voltage waveform across said high intensity discharge lamp so that said supply voltage waveform and said voltage waveform across said high intensity discharge lamp assumes a predetermined relationship during said normal mode of operation of said high intensity discharge lamp and wherein said control means provides said control signal for lighting said auxiliary lamp when said predetermined relationship does not exist.
 23. A control system according to claim 18 wherein said control means is additionally responsive to the relative amplitude of the voltage waveform across said high intensity discharge lamp and the voltage waveform from said supply voltage.
 24. A control system according to claim 18 wherein said control means is additionally responsive to the relative shape of the voltage waveform across said high intensity discharge lamp and the voltage waveform from said supply voltage.
 25. A control system according to claim 18 wherein said control means is additionally responsive to the relative amplitude and shape of the voltage waveform across said high intensity discharge lamp and the voltage waveform from said supply voltage.
 26. A control system according to claim 18 wherein said control means includes a pair of mutually coupled coils with one of said coils receiving at least a portion of said voltage waveform across said high intensity discharge lamp and the other of said coils receiving at least a portion of the voltage waveform from said supply voltage.
 27. A control system according to clAim 26 wherein one of said coils provides said control signal to said control terminal of said controlled conduction means.
 28. A control system according to claim 27 wherein the impedance through said one of said coils is high for one relative phase relationship of the voltage waveform across said high intensity discharge lamp and the voltage waveform from said supply voltage and is low for another phase relationship of the voltage waveform across said high intensity discharge lamp and the voltage waveform from said supply voltage.
 29. A control system according to claim 28 wherein said voltage waveform across said high intensity discharge lamp is out of phase with said voltage waveform from said supply voltage during said start-up mode and said cool-down mode of operation of said high intensity discharge lamp so that the impedance of said one coil is high, and said voltage waveform across said high intensity discharge lamp is in phase with said voltage waveform from said supply voltage during said normal mode of operation of said high intensity discharge lamp so that said impedance of said one coil is low, said one coil being connected to said control terminal of said controlled conduction device so as to turn on said controlled conduction device when said impedance of said one soil is high.
 30. A control system according to claim 29 including phase-shifting means connected to receive one of the voltage waveforms of said high intensity discharge lamp and said voltage waveform from said supply voltate to provide said in-phase and out-of-phase relationships.
 31. A control system according to claim 29 including phase-shifting means connected to receive said supply voltage to provide said voltage waveform from said supply voltage.
 32. A control system for an auxiliary lamp for providing supplemental lighting for a high intensity discharge lamp which is adapted to be powered by a source of supply voltage through a ballast, said ballast having first, second and third terminals with said first and third terminals being adapted to be connected to said source of supply and said second and third terminals being adapted to be connected to said high intensity discharge lamp, said high intensity discharge lamp having a normal mode of operation in which the luminescence of said high intensity discharge lamp is at a high level and start-up and cool-down modes of operation in which the luminescence of said high intensity discharge lamp is at a reduced level relative to said high level of luminescence comprising: controlled conduction means having a control terminal for receiving a control signal for connecting said auxiliary lamp to an electric power source for said auxiliary lamp to light said auxiliary lamp; and control means responsive to the voltage between said first and second terminals of said ballast for providing said control signal to said control terminal of said controlled conduction means to light said auxiliary lamp during at least portions of one of said start-up and said cool-down modes of operation of said high intensity discharge lamp whereby said auxiliary lamp provides supplemental lighting when the level of said luminescence of said high intensity discharge lamp is reduced during said one of said start-up and cool-down modes of operation of said high intensity discharge lamp.
 33. A control system according to claim 32 wherein said control means includes a coil which received said voltage between said first and second terminals of said ballast and which is responsive thereto.
 34. A control system for an auxiliary lamp for providing supplemental lighting for a high intensity discharge lamp having a normal mode of operation in which the luminescence of said high intensity discharge lamp is at a high level and start-up and cool-down modes of operation in which the luminescence of said high intensity discharge lamp is at a reduced level relative to said high level of luminescence comprising: control means for connecting said auxilIary lamp to a source of electric power for lighting said auxiliary lamp during at least portions of said start-up and said cool-down modes of operation of said high intensity discharge lamp and to provide an IR voltage drop across said auxiliary lamp, said first control means ordinarily disconnecting said auxiliary lamp from said source of electric power during said normal mode of operation of said high intensity discharge lamp; and failsafe means in addition to said control means which is connected to said auxiliary lamp and is at least in part responsive to the IR voltage drop across said auxiliary lamp for limiting simultaneous operation of said high intensity discharge lamp and said auxiliary lamp while under the control of said control means.
 35. A control system according to claim 34 wherein said failsafe means is at least in part responsive to the current through said high intensity discharge lamp.
 36. A control system according to claim 34 wherein said failsafe means includes a coil which is responsive to the IR voltage drop across said auxiliary lamp.
 37. A control system according to claim 36 wherein said coil has a core which is saturable in response to an IR voltage drop across said high intensity discharge lamp when said high intensity discharge lamp is on continuously.
 38. A control system according to claim 34 wherein said high intensity discharge lamp is adapted to be powered by a source of supply voltage through a ballast, said ballast having first, second and third terminals with said first and third terminals being adapted to be connected to said source of supply and said second and third terminals being adapted to be connected to said high intensity discharge lamp, said failsafe means being at least in part responsive to the voltage between said first and second terminals of said ballast for limiting simultaneous operation of said high intensity discharge lamp and said auxiliary lamp under control of said control means.
 39. A control system according to claim 36 wherein said failsafe means includes a temperature responsive switch which is openable upon a predetermined simultaneous operation of said high intensity discharge lamp and said auxiliary lamp to turn off said auxiliary lamp.
 40. A control system according to claim 39 wherein said failsafe means includes heating means which is responsive to the current through said auxiliary lamp for heating said temperature responsive switch when said auxiliary lamp is on.
 41. A control system according to claim 40 wherein said heating means receives a current derived from at least a portion of the IR voltage drop across said auxiliary lamp.
 42. A control system according to claim 40 wherein said heating means is a resistor.
 43. A control system according to claim 40 wherein said heating means is a coil.
 44. A control system according to claim 43 wherein said supply voltage has an alternating waveform and said auxiliary lamp continuously receives the entirety of said alternating waveform at times and receives portions of said alternating waveform at other times, and wherein said failsafe means includes a coil having a core which is saturated when said auxiliary lamp receives the entirety of said alternating waveform.
 45. A control system for an auxiliary lamp for providing supplemental lighting for a high intensity discharge lamp, said discharge lamp being connectable to a source of electric power to establish a voltage thereacross and having a normal mode of operation in which the luminescence of said high intensity discharge lamp is at a high level and start-up and cool-down modes of operation in which the luminescence of said high intensity discharge lamp is at a reduced level relative to said high level of luminescence comprising: controlled conduction means having a control terminal for receiving a control signal for connecting said auxiliary lamp to an electric power source for said auxiliary lamp to light said auxiliary lamp; and control meaNs for connection to said high intensity discharge lamp to be responsive to said start-up and cool-down modes of opeation of said high intensity discharge lamp and further being connected to receive the voltage across said auxiliary lamp to be in part responsive to the voltage across said auxiliary lamp for providing said control signal to said control terminal of said controlled conduction means to light said auxiliary lamp during at least portions of said start-up and said cool-down modes of operation of said high intensity discharge lamp whereby said auxiliary lamp provided supplemental lighting when the level of said luminescence of said high intensity discharge lamp is reduced.
 46. The control system according to claim 45 wherein said control means increases said control signal in response to a voltage across said auxiliary lamp indicating that said auxiliary lamp is lit.
 47. A control system according to claim 45 wherein said voltage across said auxiliary lamp tends to maintain the provision of said control signal to said control terminal of said controlled conduction means when said auxiliary lamp is connected to said source of electric power.
 48. A control system for an auxiliary lamp for providing supplemental lighting for a high intensity discharge lamp, said discharge lamp being connectable to a source of electric power to establish a voltage thereacross and having a normal mode of operation in which the luminescence of said high intensity discharge lamp is at a high level and start-up and cool-down modes of operation in which the luminescence of said high intensity discharge lamp is at a reduced level relative to said high level of luminescence comprising: first controlled conduction means associated with said auxiliary lamp and a source of power for said auxiliary lamp for controlling the lighting of said auxiliary lamp, said first controlled conduction means including a control terminal for causing said first controlled conduction means to conduct to connect said source of power to said auxiliary lamp to light said auxiliary lamp in response to a first control signal at said control terminal; second controlled conduction means connected to said control terminal of said first controlled conduction means, said second controlled conduction means having a control terminal and supplying said first control signal to said control terminal of said first controlled conduction means in response to a second control signal at said control terminal of said second controlled conduction means; and control means connected to said high intensity discharge lamp to be responsive to said start-up and said cool-down modes of operation of said high intensity discharge lamp for providing said second control signal to said control terminal of said second controlled conduction means so that said second controlled conduction means supplies said control signal to said control terminal of said first controlled conduction means to light said auxiliary lamp during at least portions of said start-up and said cool-down modes of operation of said high intensity discharge lamp whereby said auxiliary lamp provides supplemental lighting when the level of said luminescence of said high intensity discharge lamp is reduced.
 49. A control system according to claim 1 wherein said switch means is a reed switch. 